This invention relates to a method and apparatus for the numerical control of machining tools used in the manufacture of gears from workpieces. The invention also relates to a method for manufacturing such gears.
In machining apparatuses having numerical control devices, the motion of the workpiece is dependent on at least one kind of motion of the cutting tool. An input variable for a position control of the workpiece is derived from the actual position of the tool.
In the manufacture of gears by equipment such as hobbing machines, it is necessary that the tool and the workpiece are rotated relative to one another with a predetermined reduction ratio. Generally, the rotation of a tool (e.g., a milling cutter) is used as the control motion and the rotation of the workpiece is achieved by divider transmissions. For uniform tool wear and the production of helical gearing, the tool may be additionally moved in other directions and along other paths.
If mechanical gearing is to be avoided and electronic tracking of the workpiece relative to the tool is to be achieved, a variable proportional to the rotation of the tool is generated as the desired value in a position control loop of the workpiece. Where the tool undergoes a number of different kinds of motion, the rotation of the workpiece may be controlled in accordance with or in response to the different motions of the machine tool. Correction quantities derived from the various motions of the tool are superimposed additively.
In the electronic position control of workpiece motion, a lag occurs which is due, for example, to a difference between the desired position of the workpiece and the instantaneous actual position thereof. This lag leads to inaccuracies in the production of gearing.
An object of the present invention is to provide an improved method and apparatus for the production of gearing in a simple manner and with high accuracy.
Another, more particular, object of the present invention is to provide an improved numerical control of the above-described type.